BEIRUT, Feb 1 (Reuters) - A suicide car bomber killed four people on Saturday in a Hezbollah stronghold on Lebanon's northern border in the latest sign that Syria's civil war was spilling over into its small Mediterranean neighbour.

Lebanon's National News Agency (NNA) reported the blast occurred beside a petrol station in the town of Hermel at the northern end of the Bekaa Valley, an area populated mainly by Shi'ite Muslims among whom Hezbollah draws its support.

There was no immediate claim of responsibility but Saturday's blast fit a pattern of attacks by rival sectarian groups on each other's strongholds that has been amplified by Syria's civil war. Another suicide car bomb killed three people in Hermel last month.

A security source told Reuters that 14 other people were wounded in Saturday's blast, which was located near a building housing a charity connected to the late Shi'ite Grand Ayatollah Mohammad Hussein Fadlallah.

Fadlallah was not a member of Hezbollah, which has been the target of increasingly frequent bomb attacks in recent months.

The military and political movement has sent fighters and advisers to aid President Bashar al-Assad, a member of Syria's Alawite minority, in his battle with mainly Sunni rebels. (Reporting By Stephen Kalin; Editing by Tom Heneghan)